Analysis: Hinkley delay could put UK carbon budgets at further risk

The latest delays to the Hinkley Point C new nuclear plant could spell bad news for UK carbon budgets, Carbon Brief analysis shows.

A final investment decision on the scheme, due to be the UK’s first new nuclear plant for a generation, has just been postponed by French energy firm EDF in the latest of many delays.

Each year it fails to operate would add around 8-11 million tonnes of CO₂ to the UK’s emissions, assuming it is replaced by gas-fired generation, and depending on what proportion of hours Hinkley would have operated (see footnote).

The UK is already expected to miss its carbon budgets for the mid-2020s. The emissions from a delay at Hinkley would increase this overshoot four-fold, Carbon Brief analysis shows (red hatched area, below).

Perversely, however, this increase would be completely ignored for carbon budgeting purposes, under the UK’s current emissions accounting rules. An amendment to the Energy Bill would change the rules so that all UK territorial emissions are counted towards carbon budgets (see below).

The UK carbon budget for 2025 (grey) and projected emissions for the same year, showing an overshoot of 4MtCO₂e. Without Hinkley, the overshoot would increase to 15MtCO₂e (red), assuming the electricity it would have supplied is replaced with gas-fired generation. The increase would be lower if Hinkley runs for fewer hours, see footnote. Source: Department for Energy and Climate Change (DECC) projections for the actual UK emissions, the UK’s fourth carbon budget and Carbon Brief calculations. Chart by Carbon Brief.

The UK could instead replace the lost generation from a delay to Hinkley with zero-carbon wind. However, the requirements would be significant.

To generate as much electricity as the 3.2 gigawatt (GW) Hinkley scheme, the UK would need to build an additional 9-11GW of onshore windfarms, a total of between around 3,000 and 5,500 individual turbines, depending on turbine size. Alternatively, the UK could build 6-7GW of offshore windfarms, with around between 800 and 1,500 turbines — again depending on turbine size.

The UK currently has 8.5GW of onshore and 5GW of offshore capacity totalling 5,200 and 1,500 turbines respectively. Replacing Hinkley would take roughly as much wind capacity as the UK has in total today. Other ways to replace Hinkley are discussed in the footnote, below.

The Committee on Climate Change (CCC) says the UK would not be able to reduce power sector emissions below 100 grammes of CO₂ per kilowatt hour in 2030 without new nuclear power stations. This 100g target is a key staging point on the most cost-effective route to meeting UK carbon budgets in the long term, the CCC says. This means missing it would increase costs.

There are several new nuclear schemes in the pipeline other than Hinkley.

Footnote

The calculations above are indicative. They are based on a 3.2GW capacity for Hinkley Point C operating at an 80-100% load factor. If this were replaced by gas-fired generation, associated emissions would be 8-11MtCO₂.

Glossary

Load factor: A measure of the average output of a power station, relative to its installed capacity. This depends on technical and economic factors. For individual gas, coal or nuclear plants the load factor can in theory be above 90%. However, UK fleet-wide averages are much lower. The range of fleet-wide average load factors during 2010-2014 was 28-62% for gas, 40-57% for coal and 65-74% for nuclear. The range of rates for the UK's renewable fleets was 10-11% for solar, 22-28% for onshore and 30-38% for offshore wind. Newer windfarms tend to have larger turbines, particularly offshore, and are expected to reach load factors of up to 48%.

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Load factor: A measure of the average output of a power station, relative to its installed capacity. This depends on technical and economic factors. For individual gas, coal or nuclear plants the load factor… Read More

The UK’s existing fleet of nuclear power stations sometimes operates at much lower load factors. For instance, the average during 2014 was below 70% after a series of unexpected outages. The average load factor in 2015 is higher, though full year data is not yet available.

There is some disagreement over the most appropriate load factor to assume for Hinkley. However, it is common to assume a load factor of around 90%.

Emissions from coal-fired generation would be around 2.5-fold higher than gas, however, the UK plans to phase out coal by 2025.

The windfarm calculations assume each onshore wind turbine has a capacity of 2-3 megawatts (MW) and each turbine offshore is 5-7MW. Even larger models are available. We have assumed onshore windfarms operate with a 28% load factor and offshore at 44%. These numbers will vary according to project location and turbine size. This offshore load factor is higher than current rates but is expected for future windfarms.

Because these windfarms would not operate 100% of the time, there would need to be some back-up generation, demand-response to reduce electricity needs, or undersea interconnectors to access supplies from further afield. There may be some emissions related to operating backup less efficiently, though the evidence suggests they will be limited.

Windfarms would not be the only way to replace Hinkley. In practice it would probably be replaced with some combination of renewable and non-renewable resources, along with energy efficiency and interconnection. The mix would determine the emissions impact of Hinkley being delayed. However, it’s worth repeating that only some mixtures would be compatible with the CCC’s least-cost path to the 2050 UK carbon target.

Other options include tidal lagoons, gas- or coal-fired plant with carbon capture and storage or increased efforts towards reducing demand. The electricity output from Hinkley would be equivalent to about a fifth of current domestic demand.

Carbon accounting

For the carbon budget comparison, we took forecasts from DECC’s latest energy and emissions projections of UK territorial emissions and compared them to the net carbon budget, which we’ll come on to in a moment. Strictly speaking this comparison may not have been the most appropriate choice, as you can see if you follow this conversation on Twitter. In practice, however, a better comparator is not publicly available.

At this point, it’s worth noting a quirk of the current carbon accounting system, which is the root cause of these complications.

Under current carbon budget accounting rules, the UK does not count actual emissions from its traded sector. This is the part of the economy covered by the EU Emissions Trading System (EU ETS), including power stations and heavy industry.

Instead, the UK counts its allocation under EU ETS rules, even if some of the allocation remains unused or if actual emissions are higher. This means the UK could build 10 new coal-fired power stations without directly affecting its progress towards carbon targets.

The idea was that a UK emissions surplus or shortfall under the EU ETS would even out via trading, and so it didn’t necessarily make sense to count them when looking at the carbon budget. Using these existing accounting rules, the UK is even further behind its carbon budget for 2025, as the chart below shows.

The UK carbon budget for 2025 (grey) and projections emissions for the same year, showing an overshoot of 35MtCO₂e. Without Hinkley, the overshoot would increase to 43-46MtCO₂e (red), assuming the electricity it would have supplied is replaced with gas-fired generation and depending on the load factor. Source: Department for Energy and Climate Change (DECC) projections for the UK’s net carbon account, the UK’s fourth carbon budget and Carbon Brief calculations. Chart by Carbon Brief.

In its statutory advice on the fifth carbon budget for 2028-2032 the CCC argued that these accounting rules should change. Ensuring real emissions reductions in the traded sector is too important to the long-term success of UK carbon-cutting efforts, the CCC said.

It suggested setting a separate budget for the UK’s non-traded sector. Sandbag, the carbon markets thinktank, would like a more fundamental reform of the carbon accounting rules. It says all UK emissions ought to be counted towards carbon budgets, rather than adding the non-traded total to a fixed EU ETS allocation. This issue is explored in more detail in a briefing from the Parliamentary Office of Science and Technology.

Amendments to the Energy Bill currently going through parliament would change the UK’s carbon accounting rules in line with Sandbag’s recommendations. However, the government has moved to strike this amendment from the Bill.

Update 28/1 – In response to comments from readers we have amended various parts of this article. The opening paragraphs were amended in relation to carbon accounting rules. The remainder of the article was changed to reflect a range of load factor assumptions for Hinkley.

Update 29/1 – We added more detail on load factor ranges and wind turbine sizes.

Main image: A tractor mows a field on the site where EDF Energy’s Hinkley Point C nuclear power station will be constructed in Bridgwater, southwest England in this October 24, 2013 file photograph. The European Commission will open an investigation mid December 2014 into planned British support for a new nuclear power plant, two people familiar with the matter said, in a precedent-setting case for future nuclear funding in Europe.